Right now? Rondo. Bradley has potential to be better, but right now he has happy feet (much like Rondo had his rookie year). It didn't show up last night, because the Knicks didn't put any pressure on him, so he could shoot like its practice, but when he feels any pressure, he has terrible balance on his shot.
Rondo on the other hand has done a lot to fix that part of his shot. His footwork has improved immensely, and now he just needs to get more consistent with the finish.
I really just think Bradley has terrible fundamentals in general. He looks like a guy who dominated in highschool purely on his athleticism, and has never learned how to actually play. So, they are basically forced to break him down and start from scratch, which is both a long process, and it is very hit or miss. The talent is there, but this kid has a long way to go.